Power window pulldown circuit

ABSTRACT

Power window apparatus for opening and closing a window in accordance with the setting of a selectively operable switch. Upon placement of the switch in a window opening setting a window drive motor connected to the window is placed in a first energized condition so as to open the window. Upon placement of the switch in a window-closing setting power is supplied through a transistor to the motor so as to place the motor in a second energized condition and close the window. Should the motor be stalled by the window being closed on an obstacle the window travel is reversed by the resultant decrease in the voltage across the motor armature causing a bias network to both turn off the transistor and place the motor in the first energized condition. A limit switch that is responsive to the window position is provided to prevent the armature voltage from effecting reversal of the window when the window is substantially closed so as to allow the motor to seal the window. A time delay network is provided for preventing voltage transients generated upon starting the motor from effecting reversal of the window travel during a predetermined time.

U M9 Robbins States Patent [54] POWER WINDOW PULLDOWN [2i] Appl. No.:66,478

[52] US. CL... ..318/266, 318/297, 318/447 [51] Int. Cl. ..H02h 7/097[58] Field of Search ..318/266, 297, 447, 466, 265,

[56] References Cited UNITED STATES PATENTS 3,513,374 5/1970 Koment ..318/266 Primary Examiner-Bernard A. Gilheany Assistant ExaminerW. E.Duncanson, Jr. Attomey-Jean L. Carpenter and Paul Fitzpatrick 5] Feb.22, 1972 ABSTRACT Power window apparatus for opening and closing awindow in accordance with the setting of a selectively operable switch.Upon placement of the switch in a window opening setting a window drivemotor connected to the window is placed in a first energized conditionso as to open the window. Upon placement of the switch in awindow-closing setting power is supplied through a transistor to themotor so as to place the motor in a second energized condition and closethe window. Should the motor be stalled by the window being closed on anobstacle the window travel is reversed by the resultant decrease in thevoltage across the motor armature causing a bias network to both turn ohthe transistor and place the motor in the first energized condition. Alimit switch that is responsive to the window position is provided toprevent the armature voltage from effecting reversal of the window whenthe window is substantially closed so as to allow the motor to seal thewindow. A time delay network is provided for preventing voltagetransients generated upon starting the motor from effecting reversal ofthe window travel during a predetermined time.

6 Claims, 1 Drawing Fis' re POWER WINDOW PULLDOWN CIRCUIT This inventionrelates to power window apparatus and, more particularly, to powerwindow apparatus for use in motor vehicles.

Many diverse types of power window systems have heretofore been employedto operate the windows of motor vehicles. Though these systems are ofvarious designs their functions are basically similar inasmuch as mostof them raise and lower vehicle windows in accordance with the settingof a selectively operable switch that is manipulated by a vehicleoccupant. In addition, some of these prior art power window systems aredesigned to have a provision for reserving the direction of windowtravel when the window is being closed on an object that is positionedso as to obstruct the window. it is this latter type of power windowsystem to which the present invention relates.

While many of the power window systems presently in commercial usage andheretofore proposed are capable of carrying out their assigned functionsadmirably, the continuing interest of vehicle owners and occupants inconvenience features such as power window systems in their motorvehicles provides considerable incentive for the development of aneconomical and reliable power window design which may be adopted forwidespread consumer usage. The present invention is proposed as a meansof fulfilling this widespread need.

Accordingly, it is now proposed to open a window by direct energizationof a reversible window drive motor and to close the window by energizingthe window drive motor through a transistor. Should the motor be stalledand its armature voltage reduced by the window striking an obstaclewhile it is closing, the direction in which the motor drives the windowis reversed by biasing the transistor to its nonconductive condition andenergizing the motor through the transistor bias circuitry. A limitswitch that is responsive to the position of the window is provided forpreventing the bias circuitry from turning off the transistor andeffecting reversal of the motor when the window is substantially closedso as to allow the motor to stall while tightly sealing the windowclosed. In addition, a time delay network is provided for preventing thebias circuitry from turning off the transistor and effecting thereversal of the motor for a predetermined time after the motor begins toclose the window so as to prevent voltage transients generated uponstarting the motor from effecting reversal of the motor during thepredetermined time.

Other advantages and features of the subject invention will becomeapparent from the following description and accompanying drawing, whichschematically illustrates power window apparatus incorporating theprinciples of the subject invention.

As is shown in the drawing, a window 10, which is portrayed as a vehiclewindow that includes a window frame 12 and a windowpane 14, is openedand closed by a motor 16 which includes first and second selectivelyenergizable field windings l8 and 20 and an armature 22 that is drivablyconnected to the window through a suitable drive mechanism 24. Thoughthe drive mechanism 24 may be of any suitable type, as is apparent tothose versed in the art, it is presented in the drawing for purposes ofillustration as including a gear 26 driven by the armature 22 and a rack28 'driven by the gear 26 and connected to the windowpane 14. A controlcircuit 30 is provided for controlling the energi'zation of the windingsl8 and 20 so that when the first winding 18 is energized the motor 16opens the window 10 and when the second winding 20 is energized themotor 16 closes the window 10.

The control circuit 30 is powered by a suitable power source, such as avehicle battery 32 of a conventional design, that is in series circuitwith a vehicle ignition switch 34, which is preferably of a conventionaldesign that precludes operation of the control circuit 30 and the window10 when the vehicle ignition is turned off. Upon closure of the ignitionswitch 34 the battery 32 is connected to a switch arm 36 of aselectively operable switch 38 of the well-known and presently widelyused type in which the switch arm 36 is normally spring-biased by aspring mechanism (not shown) to the neutral center position illustratedin the drawing. When it is desired to open the window 10 a vehicleoperator manually places the switch 38 in a window opening setting byengaging a first contact 40 with the switch arm 36. To close the windowthe vehicle operator places the switch 38 in a window closing setting byengaging a second contact 42 with the switch arm 36.

Upon placement of the switch 38 in the window opening setting thebattery 32 is connected through the switch 38 and a lead 44 to the motor16 so as to energize the first winding 18 through the armature 22. Themotor 16 is thus placed in a first energized condition and opens thewindow 10.

When the switch 38 is placed in the window closing setting the battery32 is connected through the switch 38 to the emitter terminal 46 of aPNP-power-transistor 48 which has its collector terminal 50 collectedthrough a lead 52 to the second winding 20 of the motor 16. Accordingly,when the switch 38 is placed in the window closing setting and thetransistor 48 is biased so as to be in a conductive condition the secondwinding 20 is energized by the battery 32 through a current path whichincludes the switch 38, the transistor 48, and the armature 22 so as toclose the window 10.

The bias network 54 is provided to assure that the transistor 48 isnormally biased to its conductive condition when the switch 38 is placedin the window-closing setting. The bias network 54 includes a resistor56 and a diode 58 series connected between the base terminal 60 of thetransistor 48 and ground. In addition, the bias network 54 includes asilicon-controlled rectifier (SCR) 62 connected between the emitter andbase terminals 46 and 60 of the transistor 48. Since power is onlysupplied by the battery 32 to the SCR 62 when the switch 38 is in thewindow-closing setting the SCR 62 is nonconductive upon placement of theswitch 38 in the window-closing setting and remains nonconductive untila voltage signal greater than a certain value is applied to the gateterminal 64 of the SCR 62.

Upon placement of the switch 38 in the window-closing setting thevoltage at the base terminal 60 of the transistor 48 thus falls belowthe voltage at the emitter terminal 46, the precise voltage lever beingdetermined by the reverse leakage characteristics of the diode 58, andthe forward biased baseemitter junction of the transistor 48 causes thetransistor 48 to assume its conductive condition. By properly selectingthe diode 58 to have appropriate reverse leakage characteristics thebase terminal 60 of the transistor 48 is held at a relativelyhigh-voltage but is nevertheless at sufficiently low a voltage to keepthe transistor 48 fully conductive. For example, in a typicalinstallation in which the battery 32 is a l2-volt battery the baseterminal 60 of the transistor 48 may be held at about a 9- voltpotential when the transistor 48 is conductive. Accordingly, arelatively small increase in voltage at the base 60 of the transistor 48will suffice to turn off the transistor 48. The diode 58 thus helpsprotect the transistor 48 against large voltage excursions which may begenerated when switching the windings l8 and 20, as will subsequentlybecome apparent to persons versed in the art.

The conductivity of the SCR 62 is controlled in accordance with thevoltage across the armature 22 of the motor 16 so that when the window10 is closed on an obstacle the resultant stalling of the motor 16 anddecrease in the armature 22 voltage causes the generation of a voltagesignal that switches the SCR 62 to its conductive state. When the SCR 62is conductive it reverses the motor 16 and opens the window 10 bybiasing the transistor 48 to its nonconductive condition and energizingthe first winding 18, as will subsequently be explained. To this end thevoltage across the armature 22 is monitored by a voltage-monitoringnetwork 66 which includes an NPN- transistor 68, a coupling resistor 70,and suitable biasing resistors 72 and 74. When the voltage-monitoringnetwork 66 has detected that the motor 16 is stalled, it causes acontrol network 76 to generate and transmit to the gate terminal 64 ofthe SCR 62 a voltage signal of sufficient magnitude to switch the SCR 62to its conductive condition.

The control network 76 includes a unijunction transistor 78, a chargingresistor 80, a charging capacitor 82, a discharge resistor 83, acoupling resistor 84, and a second SCR 86. Power for operating thecontrol network 76 is provided by the battery 32 through the switch 38,a lead 88, and the second SCR 86 when the switch 38 is placed in thewindow-closing setting and the second SCR 86 is conductive. The controlnetwork 76 in turn provides the energization for the voltage-monitoringnetwork 66 through the transistor 68. However, it is desirable that thesupply of power to the control network 76 and the voltage-monitoringnetwork 66 be interrupted so as to prevent the switching of the SCR 62at certain times, most notably when the motor 16 stall while sealing thewindow closed and when voltage transients generated by starting themotor 16 may inadvertently cause switching of the SCR 62.

Accordingly, a normally closed limit switch 90 that is positioned so asto be responsive to the window 10 position is connected in series withthe second SCR 86 so as to interrupt power to the control network 76,and hence preclude the control network 76 from generating the requisitevoltage signal to switch the SCR 62, when the window is substantiallyclosed. The motor 16 is thus allowed to stall when the window 10 issubstantially closed so as to tightly seal the window 10 in its closedposition.

Voltage transients which may be generated upon starting the motor 16 areprevented from inadvertently switching the SCR 62 by a time delaynetwork 92, which includes a resistor 94, a timing capacitor 95, and adischarge diode 96. The time delay network 92 is supplied power by thebattery 32 through the lead 88 and controls the voltage applied to thegate terminal 97 of the second SCR 86. Upon placement of the switch 38in the window-closing setting the capacitor 95 is charged through theresistor 94. Since the capacitor 95 does not have an initial charge thesecond SCR 86 is held nonconductive for a predetermined time after theswitch 38 is placed in the window-closing setting, the time beingdetermined by the time constant of the time delay network 92. Byproperly selecting the values of the resistor 94 and the capacitor 95the second SCR 86 is kept turned off until after the voltage transientsgenerated by starting the motor 16 have died out. After thepredetermined time has elapsed the charge on the capacitor 95 issufficient to turn on the second SCR 86, which becomes conductive anddischarges the capacitor 95 through the diode 96. Since the second SCR86 must be conductive to supply power to the control network 76 the timedelay network 92 thus prevents these voltage transients from switchingthe SCR 62 during the predetermined time.

After the predetermined time has elapsed stalling of .the motor 16 whenclosing the window 10 decreases the armature 22 voltage below thecertain level that is indicative of the motor 16 being stalled. Assumingthat the window 10 is open sufficiently that the control network 76 isnot disabled by the limit switch 90, the voltage-monitoring network 66detects the low armature 22 voltage and the control network 76 generatesa voltage signal which exceeds the predetermined value so as to switchthe SCR 62 from its nonconductive to its conductive condition. When theSCR 62 is in a conductive state the voltage on the cathode 98 on the SCR62 deenergizes the second winding by turning off the transistor 48 andenergizes the first winding 18 through a diode 99, as will be explainedin the following operational description.

A vehicle occupant may operate the aforedescribed apparatus merely bychanging the setting of the switch 38. When the vehicle operator wishesto open the window 10, he places the switch 38 in the window-openingsetting by engaging the contact 40 with the switch arm 36. The battery32 is then connected in series circuit through the switch 38 and thelead 44 with the first winding 18 and the armature 22. Accordingly, themotor 16 is placed in a first energized condition in which it opensthewindow 10 until either the window 10 is fully open or the switch 38 isremoved from the window-opening setting.

When a vehicle occupant desires to close the window 10 he places theswitch 38 in the window closing setting by engaging the second contact42 with the switch arm 36. The full voltage of the battery 32 is thenapplied through the switch 38 to the emitter of the transistor 48 and,through the lead 88, to both of the SCRs 62 and 86 and the time delaynetwork 92. Since the timing capacitor is not initially charged, thegate terminal 97 of the second SCR 86 is initially at ground potentialwhen the switch 38 is placed in the window-closing setting. The secondSCR 86 is thus initially held in its nonconductive condition and thecontrol network 76 is precluded from applying a voltage signal to thegate terminal 64 of the SCR 62 that would switch the SCR 62 to itsconductive condition. The I SCR 62 therefore initially remainsnonconductive so as to bias the transistor 48 to its conductivecondition. Accordingly, as soon as the switch 38 is placed in thewindow-closing setting, the second winding 20 is energized through thetransistor 48 and the armature 22 so as to cause the motor 16 to closethe window 10.

At a predetermined time after the switch 38 is placed in thewindow-closing setting, the time being determined by appropriateselection of the resistor 94 and the timing capacitor 95, the voltageacross the capacitor 95 is sufficient to turn on the second SCR 86. Whenthe second SCR 86 is turned on it discharges the capacitor 95 throughthe diode 96 and allows the passage of a current from the lead 88through the second SCR 86, the normally closed limit switch 90, thecoupling resistor 84, the resistor 80, and the capacitor 82. Thiscurrent tends to charge the capacitor 82 to a level sufficient to turnon the unijunction transistor 78 but the voltage-monitoring network 66continuously drains the charge from the capacitor 82, keeping theunijunction transistor 78 nonconductive.

As persons versed in the art will appreciate, the voltage across thearmature 22 is proportional to the speed of the motor 16. Accordingly,when the motor 16 is closing the window 10 the lead 44 and the firstwinding 18 are substantially at the potential of the voltage across thearmature 22. The armature 22 voltage is thus sensed by thevoltage-monitoring network 66 through the first winding 18 and thecoupling resistor 70, which applies the armature voltage to the baseterminal of the transistor 68. By properly biasing the transistor 68with the resistors 72 and 74 the voltage which is applied from thearmature 22 to the base terminal of the transistor 68 when the win- .dow10 is being closed is sufficient to turn on the transistor 68,

which drains the charge from the capacitor 82 so as to prevent theturning on of the unijunction transistor 78. Accordingly, theunijunction transistor 78 normally remains nonconductive and the voltageon the gate terminal 64 of the SCR 62 is insufficient to turn on the SCR62.

Howevenshould the window 10 be closed upon an obstacle which stalls themotor 16 theresultant decrease in the armature 22 speed causes acorresponding decrease in the voltage across the armature 22. When thearmature 22 voltage has fallen below a certain level the potentialapplied to the base terminal of the transistor 68 is insufficient tomaintain the transistor 68 conductive. Accordingly, thevoltage-monitoring network senses that the motor 16 is stalled bytheturning off of the transistor 68 and allows the capacitor 82 toaccumulate a charge sufficient to turn on the unijunction transistor 78.When the unijunction transistor 78 is turned on some of the power beingsupplied through the second SCR 86 is diverted through the unijunctiontransistor 78, so as to generate a large voltage signal across thedischarge resistor 83. The voltage signal is applied to the gateterminal 64 of the SCR 62 and is of sufficient magnitude to switch theSCR 62 to its conductive condition. Due to the inherent latchingcharacteristic of SCRs such as the SCR 62 the SCR 62 remains conductiveso long as its supply of energy from the battery 32 through the switch38 remains uninterrupted.

Upon switching the SCR 62 to its conductive condition substantially thesame potential is applied through the SCR 62 to the base terminal 60 ofthe transistor 48 as is applied to the emitter terminal 46 of thetransistor 48. The voltage across the emitter-base junction of thetransistor 48 is thus insufficient to maintain the transistor 48conductive so that itis switched to its nonconductive condition, causingthe resultant deenergization of the second winding 20. Subsequentclosure of the window by the motor 16 after the motor 16 is stalled isthus precluded by switching the transistor 48 to its nonconductivecondition.

When the SCR 62 is switched to its conductive state, it also supplies alarge current through the diode 99 and the lead 44 to the first winding18, causing the energization of the first winding 18 through thearmature 22. Since the second winding 20 is deenergized simultaneouslywith the energization of the first winding 18 through the bias network54, the direction in which the motor 16 drives the window 10 is reversedso as to open the window 10 as soon as its closure on an obstacle hasbeen detected by the voltage-monitoring network 66. Furthermore, thelatching of the SCR 62 in its conductive condition causes the firstwinding 18 to remain energized through the bias network 54 and the diode99 so long as power is supplied to the SCR 62 by holding the switch 38in the windowclosing setting. The window 10 will therefore be openedeither until it is fully opened or the vehicle operator releases theswitch 38.

Should the window 10 not encounter an obstacle while being closed themotor 16 does not stall but rather drives the window 10 to its fullyclosed position. When the window 10 is substantially closed it opens thelimit switch 90. Since power is only supplied to the control network 76through the limit switch 90, opening of the limit switch 90 prevents thecontrol network 76 from effecting reversal of the motor 16 by switchingthe SCR 62. The motor 16 is thus allowed to stall while tightly sealingthe window 10 closed.

While the foregoing description and the drawing are directed toward thepreferred embodiment of the present invention, persons versed in the artwill appreciate that various modifications in the subject apparatus maybe made without departing from the spirit of the invention.

I claim as my invention:

1. Apparatus for opening and closing a window comprising, incombination, a power source, a reversible electric motor having anarmature drivably coupled to the window for opening and closing thewindow, a selectively operable switch having at least window-opening andwindow-closing settings, the selectively operable switch connecting themotor and the power source in series circuit when placed in thewindowopening setting effective to place the motor in a first energizedcondition so as to open the window, a power switch having conductive andnonconductive conditions connected in series circuit with the powersource and the motor by the selectively operable switch when theselectively operable switch is in the window-closing setting, biasingmeans for normally biasing the power switch to its conductive conditioneffective to place the motor in a secondenergized condition so as toclose the window when the selectively operable switch is in thewindowclosing setting, means for monitoring the voltage across the motorarmature when the motor is in the second energized condition and forcontrolling the biasing means in accordance with the monitored voltageeffective to place the power switch in its nonconductive condition whenthe monitored voltage has fallen below a predetermined level indicativeof the motor being stalled and effective to maintain the power switch inits nonconductive condition until the selectively operable switch isremoved from the window-closing setting, and means responsive to thebiasing means for effecting energization of the motor through thebiasing means so as to place the motor in the first energized conditionso long as the biasing means maintains the power switch in itsnonconductive condition whereby stalling of the motor while the windowis being closed effects reversal of the window travel.

2. Apparatus for opening and closing a window comprising, incombination, a power source, a reversible electric motor having anarmature drivably coupled to the window for opening andclosing thewindow, a selectively operable switch having at least window-opening andwindow-closing settings, the selectively operable switch connecting themotor and the power source in series circuit when placed in thewindowopening setting effective to place the motor in a first energizedcondition so as to open the window, a power switch having conductive andnonconductive conditions connected in series circuit with the powersource and the motor by the selectively operable switch when theselectively operable switch is in the window-closing setting, biasingmeans for normally biasing the power switch to its conductive conditioneffective to place the motor in a second energized condition so as toclose the window when the selectively operable switch is in thewindowclosing setting, means for monitoring the voltage across the motorarmature when the motor is in the second energized condition and forcontrolling the biasing means in accordance with the monitored voltageeffective to place the power switch in its nonconductive condition whenthe monitored voltage has fallen below a predetermined level indicativeof the motor being stalled and to maintain the power switch in itsnonconductive condition until the selectively operable switch is removedfrom the window closing setting, means responsive to the biasing meanseffective to energize the motor through the biasing means so as to placethe motor in the first energized condition so long as the biasing meansmaintains the power switch in its nonconductive condition wherebystalling of the motor while the window is being closed effects reversalof the window travel, and means responsive to the window positioneffective to prevent the biasing means from placing the power switch inits nonconductive condition when the window is substantially closed,thereby allowing the motor to seal the window closed and preventing thestalling of the motor while sealing the window closed from effectingreversal of the window travel.

3. Apparatus for opening and closing a window comprising, incombination, a power source, a reversible electric motor having anarmature drivably coupled to the window for opening and closing thewindow, a selectively operable switch having at least window-opening andwindow-closing settings, the selectively operable switch connecting themotor and the power source in series circuit when placed in thewindowopening setting effective to place the motor in a first energizedcondition so as to open the window, a power switch having conductive andnonconductive conditions connected in series circuit with the powersource and the motor by the selectively operable switch when theselectively operable switch is in the window-closing setting, biasingmeans for normally biasing the power switch to its conductive conditioneffective to place the motor in a second energized condition so as toclose the window when the selectively operable switch is in thewindowclosing setting, means for monitoring the voltage across the motorarmature when the motor is in the second energized condition and forcontrolling the biasing means in accordance with the monitored voltageeffective to place the power switch in its nonconductive condition whenthe monitored voltage has fallen below a predetermined level indicativeof the motor being stalled and to maintain the power switch in itsnonconductive condition until the selectively operable switch is removedfrom the window-closing setting, means responsive to the biasing meanseffective to energize the motor through the biasing means so as to placethe motor in the first energized condition so long as the biasing meansmaintains the power switch in its nonconductive condition wherebystalling of the motor while the window is being closed effects reversalof the window travel, and time delay means for preventing the biasingmeans from being controlled in accordance with the monitored armaturevoltage for a predetermined time after the selectively operable switchis placed in the window-closing setting so as to prevent reversal of thewindow travel during the predetermined time, thereby preventing voltagetransients generated upon starting the motor from effecting reversal ofthe window travel during the predetermined time.

4. Apparatus for opening and closing a window comprising, incombination, a power source, a motor having first and second selectivelyenergizable field windings and an armature drivably coupled to thewindow for opening and closing the window in accordance with theenergization of the windings, a transistor having conductive andnonconductive conditions, a selectively operable switch having awindow-opening setting in which the switch connects the power source inseries circuit with the first winding effective to open the window and awindow-closing setting in which the switch connects the power source inseries circuit with the transistor and the second winding, a biasnetwork for controlling the conductivity of the transistor, thetransistor normally being biased to its conductive condition by thebiasing network so as to effect energization of the second winding bythe power source when the switch is placed in the window-closingsetting, and means for deenergizing the second winding and energizingthe first winding when the voltage across the armature has fallen belowa certain predetermined level indicative of the motor being stalled dueto the window encountering an obstacle while closing, said meansincluding monitoring means for detecting stalling of the motor when thewindow is being closed by monitoring the voltage across the armature,means for controlling the biasing of the transistor by the bias networkin accordance with the monitored voltage whereby the bias net- 4 workmaintains the transistor in its conductive condition until the voltageacross the armature has fallen below the certain level and thereaftermaintains the transistor in its nonconductive condition by changing thebias applied to the transistor, means for energizing the first windingso long as the bias net work maintains the transistor nonconductive,thereby reversing the window travel, means responsive to the windowposition for preventing the bias network from biasing the transistor toits nonconductive condition when the window is substantially closed soas to allow the motor to stall while sealing the window closed withouteffecting reversal of the window travel, and time delay means forpreventing the bias network from biasing the transistor to itsnonconductive condition for a predetermined time after the switch isplaced in the window-closing setting so as to prevent voltage transientsgenerated upon starting the motor from effecting a change in theenergization of the windings during the predetermined time.

5. Apparatus for opening and closing a window comprising, incombination, a motor having first and second selectively operable fieldwindings and an armature drivably connected to the window effective toopen the window when the first winding is energized and close the windowwhen the second winding is energized, a power source, a transistorhaving conductive and nonconductive conditions, a window-controllingswitch having at least a window-opening setting in which the switchconnects the power source to the motor effective to energize the firstwinding so as to open the window and a window-closing setting in whichthe switch connects the power source to the motor through the transistoreffective when the transistor is conductive to energize the secondwinding so as to close the window, a bias network for controlling theconductivity of the transistor, the bias network including a controlledrectifier responsive to a voltage signal and effective upon placement ofthe switch in the window-closing setting to bias the transistor to itsconductive condition when the voltage signal is below a certain valueand to bias the transistor to its nonconductive condition when thevoltage signal is above the certain value, the controlled rectifierkeeping the transistor biased to its nonconductive condition until theswitch is removed from the window-closing setting, means for couplingthe controlled rectifier to the motor effective to energize the firstwinding whenever the controlled rectifier biases the transistor to itsnonconductive condition, thereby reversing the direction in which themotor drives the window, a voltagemonitoring network for monitoring thevoltage across the armature when the second winding is energized so asto detect stallin'g'of the motor, the monitored armature voltage fallingbelow a certain level when the motor is stalled, a control networkresponsive to the voltage-monitoring network for generating the voltagesignal in accordance with the monitored armature voltage, the voltagesignal being below the certam value when the motor is not stalled andabove the certain value when the motor is stalled, thereby reversing thedirection in which the motor drives the window upon stalling of themotor, a limit switch responsive to the window position for preventingthe control network from generating the voltage signal when the windowis substantially closed, thereby allowing the motor to stall whilesealing the window without effecting reversal of the window travel, anda time delay network for preventing the control network from generatingthe voltage signal for a predetermined time after the window-controllingswitch is placed in the window-closing setting so as to prevent voltagetransients caused by starting the motor from effecting reversal of themotor during the predetermined time.

6. Apparatus for opening and closing a window comprising, incombination, a reversible electric motor having first and secondselectively energizable field windings and an armature drivablyconnected to the window effective to open the window when the firstwinding is energized and close the window when the second winding isenergized, a power source, a transistor having a control terminal andconductive and nonconductive conditions, a selectively operable switchhaving at least a window-opening setting in which the switch connectsthe power source to the motor effective to energize the first winding soas to open the window and a window-closing setting in which the switchconnects the power source to the motor through the transistor effectiveto energize the second winding so as to close the window when thetransistor is in its conductive condition, a bias network forcontrolling the conductivity of the transistor for controlling thevoltage applied-to the control terminal of the transistor, the biasnetwork including a controlled rectifier having anode and cathodeterminals connected between the switch and the control terminal of thetransistor and a gate terminal so as to bias the transistor to itsconductive condition when the controlled rectifier is nonconductive andto its nonconductive condition when the controlled rectifier isconductive, the controlled rectifier normally being nonconductive andbeing latched in its conductive state upon application of a voltagesignal larger than a certain value to the gate terminal, a diodeconnected between the control terminal of the transistor and the motorfor effecting energization of the first winding by the power sourcethrough the controlled rectifier and the diode when the controlledrectifier is in its conductive state, thereby reversing the direction inwhich the motor drives the window when the voltage signal exceeds thecertain value, a voltage-monitoring network for detecting stalling ofthe motor by monitoring the voltage across the armature, the armaturevoltage falling below a predetermined level when the motor is stalled, acontrol network responsive to the voltage-monitoring network forgenerating the voltage signal in accordance with the voltage across thearmature, the voltage signal being below the certain value when themotor is not stalled and above the certain value when the motor isstalled, stalling of the motor when the window is being closed therebyeffecting reversal of the direction in which the motor drives thewindow, a limit switch that is responsive to the window positioneffective to prevent the control network from generating a voltagesignal greater than the certain value when the window is substantiallyclosed so as to prevent stalling of the motor when sealing the windowclosed from effecting reversal of the direction in which the motordrives the window, and a time delay network for preventing the controlnetwork from generating a voltage signal greater than the certain valuefor a predetermined time after the selectively operable switch is placedin the windowclosing setting so as to prevent voltage transientsgenerated by starting the motor from effecting reversal of the directionin which the motor drives the window during the predetermined time.

1. Apparatus for opening and closing a window comprising, incombination, a power source, a reversible electric motor having anarmature drivably coupled to the window for opening and closing thewindow, a selectively operable switch having at least window-opening andwindow-closing settings, the selectively operable switch connecting themotor and the power source in series circuit when placed in thewindow-opening setting effective to place the motor in a first energizedcondition so as to open the window, a power switch having conductive andnonconductive conditions connected in series circuit with the powersource and the motor by the selectively operable switch when theselectively operable switch is in the window-closing setting, biasingmeans for normally biasing the power switch to its conductive conditioneffective to place the motor in a second energized condition so as toclose the window when the selectively operable switch is in thewindow-closing setting, means for monitoring the voltage across themotor armature when the motor is in the second energized condition andfor controlling the biasing means in accordance with the monitoredvoltage effective to place the power switch in its nonconductivecondition when the monitored voltage has fallen below a predeterminedlevel indicative of the motor being stalled and effective to maintainthe power switch in its nonconductive condition until the selectivelyoperable switch is removed from the window-closing setting, and meansresponsive to the biasing means for effecting energization of the motorthrough the biasing means so as to place the motor in the firstenergized condition so long as the biasing means maintains the powerswitch in its nonconductive condition whereby stalling of the motorwhile the window is being closed effects reversal of the window travel.2. Apparatus for opening and closing a window comprising, incombination, a power source, a reversible electric motor having anarmature drivably coupled to the window for opening and closing thewindow, a selectively operable switch having at least window-opening andwindow-closing settings, the selectively operable switch connecting themotor and the power source in series circuit when placed in thewindow-opening setting effective to place the motor in a first energizedcondition so as to open the window, a power switch having conductive andnonconductive conditions connected in series circuit with the powersource and the motor by the selectively operable switch when theselectively operable switch is in the window-closing setting, biasingmeans for normally biasing the power switch to its conductive conditioneffective to place the motor in a second energized condition so as toclose the window when the selectively operable switch is in thewindow-closing setting, means for monitoring the voltage across themotor armature when the motor is in the second energized condition andfor controlling the biasing means in accordance with the monitoredvoltage effective to place the power switch in iTs nonconductivecondition when the monitored voltage has fallen below a predeterminedlevel indicative of the motor being stalled and to maintain the powerswitch in its nonconductive condition until the selectively operableswitch is removed from the window closing setting, means responsive tothe biasing means effective to energize the motor through the biasingmeans so as to place the motor in the first energized condition so longas the biasing means maintains the power switch in its nonconductivecondition whereby stalling of the motor while the window is being closedeffects reversal of the window travel, and means responsive to thewindow position effective to prevent the biasing means from placing thepower switch in its nonconductive condition when the window issubstantially closed, thereby allowing the motor to seal the windowclosed and preventing the stalling of the motor while sealing the windowclosed from effecting reversal of the window travel.
 3. Apparatus foropening and closing a window comprising, in combination, a power source,a reversible electric motor having an armature drivably coupled to thewindow for opening and closing the window, a selectively operable switchhaving at least window-opening and window-closing settings, theselectively operable switch connecting the motor and the power source inseries circuit when placed in the window-opening setting effective toplace the motor in a first energized condition so as to open the window,a power switch having conductive and nonconductive conditions connectedin series circuit with the power source and the motor by the selectivelyoperable switch when the selectively operable switch is in thewindow-closing setting, biasing means for normally biasing the powerswitch to its conductive condition effective to place the motor in asecond energized condition so as to close the window when theselectively operable switch is in the window-closing setting, means formonitoring the voltage across the motor armature when the motor is inthe second energized condition and for controlling the biasing means inaccordance with the monitored voltage effective to place the powerswitch in its nonconductive condition when the monitored voltage hasfallen below a predetermined level indicative of the motor being stalledand to maintain the power switch in its nonconductive condition untilthe selectively operable switch is removed from the window-closingsetting, means responsive to the biasing means effective to energize themotor through the biasing means so as to place the motor in the firstenergized condition so long as the biasing means maintains the powerswitch in its nonconductive condition whereby stalling of the motorwhile the window is being closed effects reversal of the window travel,and time delay means for preventing the biasing means from beingcontrolled in accordance with the monitored armature voltage for apredetermined time after the selectively operable switch is placed inthe window-closing setting so as to prevent reversal of the windowtravel during the predetermined time, thereby preventing voltagetransients generated upon starting the motor from effecting reversal ofthe window travel during the predetermined time.
 4. Apparatus foropening and closing a window comprising, in combination, a power source,a motor having first and second selectively energizable field windingsand an armature drivably coupled to the window for opening and closingthe window in accordance with the energization of the windings, atransistor having conductive and nonconductive conditions, a selectivelyoperable switch having a window-opening setting in which the switchconnects the power source in series circuit with the first windingeffective to open the window and a window-closing setting in which theswitch connects the power source in series circuit with the transistorand the second winding, a bias network for controlling the conductivityof the transistor, the transistor normally being biased tO itsconductive condition by the biasing network so as to effect energizationof the second winding by the power source when the switch is placed inthe window-closing setting, and means for deenergizing the secondwinding and energizing the first winding when the voltage across thearmature has fallen below a certain predetermined level indicative ofthe motor being stalled due to the window encountering an obstacle whileclosing, said means including monitoring means for detecting stalling ofthe motor when the window is being closed by monitoring the voltageacross the armature, means for controlling the biasing of the transistorby the bias network in accordance with the monitored voltage whereby thebias network maintains the transistor in its conductive condition untilthe voltage across the armature has fallen below the certain level andthereafter maintains the transistor in its nonconductive condition bychanging the bias applied to the transistor, means for energizing thefirst winding so long as the bias network maintains the transistornonconductive, thereby reversing the window travel, means responsive tothe window position for preventing the bias network from biasing thetransistor to its nonconductive condition when the window issubstantially closed so as to allow the motor to stall while sealing thewindow closed without effecting reversal of the window travel, and timedelay means for preventing the bias network from biasing the transistorto its nonconductive condition for a predetermined time after the switchis placed in the window-closing setting so as to prevent voltagetransients generated upon starting the motor from effecting a change inthe energization of the windings during the predetermined time. 5.Apparatus for opening and closing a window comprising, in combination, amotor having first and second selectively operable field windings and anarmature drivably connected to the window effective to open the windowwhen the first winding is energized and close the window when the secondwinding is energized, a power source, a transistor having conductive andnonconductive conditions, a window-controlling switch having at least awindow-opening setting in which the switch connects the power source tothe motor effective to energize the first winding so as to open thewindow and a window-closing setting in which the switch connects thepower source to the motor through the transistor effective when thetransistor is conductive to energize the second winding so as to closethe window, a bias network for controlling the conductivity of thetransistor, the bias network including a controlled rectifier responsiveto a voltage signal and effective upon placement of the switch in thewindow-closing setting to bias the transistor to its conductivecondition when the voltage signal is below a certain value and to biasthe transistor to its nonconductive condition when the voltage signal isabove the certain value, the controlled rectifier keeping the transistorbiased to its nonconductive condition until the switch is removed fromthe window-closing setting, means for coupling the controlled rectifierto the motor effective to energize the first winding whenever thecontrolled rectifier biases the transistor to its nonconductivecondition, thereby reversing the direction in which the motor drives thewindow, a voltage-monitoring network for monitoring the voltage acrossthe armature when the second winding is energized so as to detectstalling of the motor, the monitored armature voltage falling below acertain level when the motor is stalled, a control network responsive tothe voltage-monitoring network for generating the voltage signal inaccordance with the monitored armature voltage, the voltage signal beingbelow the certain value when the motor is not stalled and above thecertain value when the motor is stalled, thereby reversing the directionin which the motor drives the window upon stalling of the motor, a limitswitch responsive to thE window position for preventing the controlnetwork from generating the voltage signal when the window issubstantially closed, thereby allowing the motor to stall while sealingthe window without effecting reversal of the window travel, and a timedelay network for preventing the control network from generating thevoltage signal for a predetermined time after the window-controllingswitch is placed in the window-closing setting so as to prevent voltagetransients caused by starting the motor from effecting reversal of themotor during the predetermined time.
 6. Apparatus for opening andclosing a window comprising, in combination, a reversible electric motorhaving first and second selectively energizable field windings and anarmature drivably connected to the window effective to open the windowwhen the first winding is energized and close the window when the secondwinding is energized, a power source, a transistor having a controlterminal and conductive and nonconductive conditions, a selectivelyoperable switch having at least a window-opening setting in which theswitch connects the power source to the motor effective to energize thefirst winding so as to open the window and a window-closing setting inwhich the switch connects the power source to the motor through thetransistor effective to energize the second winding so as to close thewindow when the transistor is in its conductive condition, a biasnetwork for controlling the conductivity of the transistor forcontrolling the voltage applied to the control terminal of thetransistor, the bias network including a controlled rectifier havinganode and cathode terminals connected between the switch and the controlterminal of the transistor and a gate terminal so as to bias thetransistor to its conductive condition when the controlled rectifier isnonconductive and to its nonconductive condition when the controlledrectifier is conductive, the controlled rectifier normally beingnonconductive and being latched in its conductive state upon applicationof a voltage signal larger than a certain value to the gate terminal, adiode connected between the control terminal of the transistor and themotor for effecting energization of the first winding by the powersource through the controlled rectifier and the diode when thecontrolled rectifier is in its conductive state, thereby reversing thedirection in which the motor drives the window when the voltage signalexceeds the certain value, a voltage-monitoring network for detectingstalling of the motor by monitoring the voltage across the armature, thearmature voltage falling below a predetermined level when the motor isstalled, a control network responsive to the voltage-monitoring networkfor generating the voltage signal in accordance with the voltage acrossthe armature, the voltage signal being below the certain value when themotor is not stalled and above the certain value when the motor isstalled, stalling of the motor when the window is being closed therebyeffecting reversal of the direction in which the motor drives thewindow, a limit switch that is responsive to the window positioneffective to prevent the control network from generating a voltagesignal greater than the certain value when the window is substantiallyclosed so as to prevent stalling of the motor when sealing the windowclosed from effecting reversal of the direction in which the motordrives the window, and a time delay network for preventing the controlnetwork from generating a voltage signal greater than the certain valuefor a predetermined time after the selectively operable switch is placedin the window-closing setting so as to prevent voltage transientsgenerated by starting the motor from effecting reversal of the directionin which the motor drives the window during the predetermined time.